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Power Vent Motor Failure (Maybe)

DocfletcherDocfletcher Member Posts: 475
edited October 2014 in Gas Heating
So tonight I oiled the cups on the motor. When I turned the boiler back on it tried to start, then I noticed the motor froze, just humming. This never happened before after oiling (2 times per year). So I think the motor is on it's way out. I let it sit with boiler off for 10 minutes and upon powering it it worked fine.

Comments

  • SWEISWEI Member Posts: 7,356
    What kind of pump and what type of oil?
  • DocfletcherDocfletcher Member Posts: 475
    Power vent motor. Automobile engine oil # 20W
  • DocfletcherDocfletcher Member Posts: 475
    It's the vent motor on A WeilMclain GV4. NG boiler.
  • SWEISWEI Member Posts: 7,356
    Sorry -- missed the title and assumed this was a circulator. Detergent or non-detergent oil? Sleeve bearings suffer when lubricated with detergent oil.
  • DocfletcherDocfletcher Member Posts: 475
    Well I'm pretty sure it was detergent oil. I gotta check the manual now. I'm fairly sure they say 20 weight, but do not specify non detergent. The reason I oiled it was because it was making noise when starting and seemed to pick up speed slowly.
  • DocfletcherDocfletcher Member Posts: 475
    edited October 2014
    SAE 20 oil. No mention of detergent or not. But it's not noisy now so maybe OK.
  • DocfletcherDocfletcher Member Posts: 475
    Well, it failed again last early this morning. After several restart attempts it worked. Based on a older thread here on heating help it was said the replacing only the motor is not recommended. Does any one here have experience with swapping out just the motor? I am most concerned with getting the shaft out of the collar.

    http://forum.heatinghelp.com/discussion/138243/weil-mclain-gv-gold-blower-motor-removal

  • SpenceSpence Member Posts: 316
    You can rotate the damper shaft at the flat end manually to keep the heat on if you haven't already. Make sure your draft is OK to ensure there isn't a furry one inside. I think it best to replace the unit and not just the motor if it has truly gone south.
  • DocfletcherDocfletcher Member Posts: 475
    edited October 2014
    Thanks. It's odd that this problem happened after oiling the motor. There is some sort of start capacitor on it and I can't help but wonder if that's the real problem. The whole assembly is pricey. Ouch!

    The set screw collar is exposed so if/when it happens again I'll give it a spin as you say. Heats on, the family is taking showers, and everything seems normal. At least for now.

  • SpenceSpence Member Posts: 316
    I missed earlier that this is a condensing boiler. The motor does double-duty; sending flue gasses into a HE to squeeze out more heat and then pushing the waste gasses into the PVC vent system.

    These units are controlled (usually) by pressure switches. If the motor starts then comes off-line, you may have a restriction in the vent piping or in the secondary HE. The pressure switches will tell the story. They should have their open or close pressure stamped on the body. Get some plastic tees and vacuum hose from your auto parts house and plug into the line (the hose will save you from cutting the factory tubing) with your manometer. If, for example, the vent switch is supposed to stay closed at .45 IWC and it opens at .25 IWC, you should be looking for vent system restrictions (drain, sagging PVC, dirty venter wheel, water in HE, incorrect termination, etc.).

    I could be incorrect, but usually those motors have run caps rather than start caps, and they can indeed fail. Check the microfarad rating on the case. With the motor running, read voltage across the two terminals (careful; this could be very high). Multiply this voltage by 2750 and divide that answer by the ACTUAL operating voltage (no, reading the nameplate isn't right). This results in microfarads, which should be within 10% of the rating marked on the can.
  • billtwocasebilltwocase Member Posts: 2,385
    edited October 2014
    You should only be using SWG Superlube. This is a synthetic oil for temp ranges from -40 to 300 degrees. You probably have an older model, and those were not capacitor start. What model do you have? The newer stainless models are not compatible with the older square plate units. This may not be an SWG. If so, disregard.
  • DocfletcherDocfletcher Member Posts: 475
    Thanks for the assistance ... :) Well, It just failed again. Try's to spin at start up, you can see the set screw collar try to turn but not able to get rotation going. I gave it an spin assist by helping it get going with my finger. That's all it takes. to get it working. Once it's in motion it stays on. Does not quit in middle of boiler heat cycle.

    I turned boiler off for 5 minutes then went and tried to rotate the set screw collar and it was seized. I was able to turn it after putting a little effort effort into it, still just using my finger.

  • SpenceSpence Member Posts: 316
    Do your cap check. Sounds as if it may be giving you trouble.
  • DocfletcherDocfletcher Member Posts: 475
    edited October 2014
    Here is cap. My son has my fluke so as soon as he comes home I'll check it. It has no tolerance on it so I think if measures real close it will be OK. Years ago I was taught if no tolerance given then 10% it will be. But that might have been for resisters. :)

    http://screencast.com/t/66AG4Ebjj
  • SpenceSpence Member Posts: 316
    Remember the cap must be wired to the motor and the motor has to be running. And remember to be careful putting your probes on the two terminals; a capacitor can easily store 3x the operating juice. That little venter may have a 3 MFD or less, so your calculation should be within 10% +/- whatever it really is.
  • DocfletcherDocfletcher Member Posts: 475
    Got my Fluke but to my dismay the it does not have capacitor capability so I mounted the cap back on the motor till I borrow or get one. However, I don't think that is the problem because afterwards I tried to rotate the shaft & collar but could barely budge it with my finger. To me it felt like it was gummed up.
  • SpenceSpence Member Posts: 316
    Go over the formula again. You just need to read volts.
  • DocfletcherDocfletcher Member Posts: 475
    My bad! Will do and thanks
  • SpenceSpence Member Posts: 316
    Good luck!
  • DocfletcherDocfletcher Member Posts: 475
    241V accross the cap
  • DocfletcherDocfletcher Member Posts: 475
    The formula seems to suggest 5.5mf 5523
  • SpenceSpence Member Posts: 316
    edited October 2014
    Divide by 2750, then multiply by the ACTUAL operating voltage to get your MFD.
  • DocfletcherDocfletcher Member Posts: 475
    Ok, that way I get 10mf. Does not seem right. I must be doing it wrong.
  • DocfletcherDocfletcher Member Posts: 475

    You should only be using SWG Superlube. This is a synthetic oil for temp ranges from -40 to 300 degrees. You probably have an older model, and those were not capacitor start. What model do you have? The newer stainless models are not compatible with the older square plate units. This may not be an SWG. If so, disregard.

    On the motor itself it calls for Anderal 465 but on the cover instructions it says use SAE 20 ONLY. So I don't know whats correct. All I know is the problem began when I oiled the cups. The way I got it going again so I could measure the voltage across the cap was to flush the bearings and whatever they lead to with brake parts cleaner via the lube tubes. Then lubed with IBM synthetic oil. It was old, from when I retired but desperate men take desperate measures. No problem since but that don't mean there won't be.
    I ordered the Anderal from Ebay and should have it Friday. I don't plan on putting anymore oil in. Thanks to all for your help. :)
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